SCARBO kicked-off its activities in December 2017 and ended in November 2021. The project covered many activities: End Users, Sensors concepts, System concept, Airborne campaign, Performance assessment, Exploitation & Use Cases and Coordination & Communication.
End Users activities identified the most promising users as Cities, with a growing importance of local issues; National/regional governments, in support of international agreements; Oil & gas sector for monitoring of GHG emission data; and Scientific community to establish accurate GHG fluxes budgets. A set of Level 2 mission requirements for CO2 and CH4 were derived (XCO2 Random Error < 1 ppm and Relative Systematic Error < 0.5 ppm; Horizontal Resolution grid size < 6 km2; Swath > 240 km and sub-daily temporal coverage at mid-latitudes).
Sensor concepts activities included the design of the NanoCarb instrument and the SPEXone support instrument. Trade-off analyses were carried out on the instrument optical design, spectral bands, performance estimation, etc. The team managed to solve feasibility issues and to raise the sensor technology from TRL2 to close to TRL5 with a prototype ready to fly on an airborne campaign. An aerosol instrument concept, based on SPEXone developed for the NASA PACE mission, was analysed to reach polarimetric and radiometric accuracy levels. System concept activities elaborated a constellation of 24 satellites offering both intraday and local time diversity, with small satellites (100 kg) embarking both NanoCarb and SPEXone instruments, launched incrementally in two batches. A demonstration airborne campaign with NanoCarb and SPEXairborne prototypes took place in October 2020, with 4 science flights focusing on aerosol retrieval flying over AERONET sites and CO2 plume detection (Belchatow, Poland). Unfortunately, cloud contamination hampered the actual detection of the CO2 plume over Belchatow. The SPEX airborne aerosol retrievals were of sufficient quality to provide light path corrections for XCO2 retrievals. CO2 NanoCarb retrievals were performed over a test scene and results demonstrated that Nanocarb can be operated with good stability, offering a strong basis for the future space concept.
A performance processing chain was developed to assess random/systematic errors, vertical sensitivities of the CO2 total columns and the full data processing chain (L0 to L2). This was done successfully and the benefits of combining SPEX + NanoCarb measurements to reduce the scattering errors has been proven. Besides, a large number of observations worldwide offered by a constellation was considered as a real asset for L4 performances.
At last, the exploitation of SCARBO was analysed and its market interest in a GHG monitoring service was assessed. Use cases were evaluated and implemented through a web interface showing L2/L4 products to illustrate SCARBO mission added value. Contacted stakeholders expressed a real interest in the services provided by SCARBO, with key characteristics lying in the measurement frequency, coverage, and spatial resolution.
Besides the main activities, 3 workshops with a User Advisory Board (UAB) were organised in the course of the project. Members of the board included key people from International and National Space Agencies, European Commission, CAMS, Regional/Local Institutions and Downstream Industry. They provided advice on various aspects of the project (user requirements, SCARBO’s position in the European and international context, etc). SCARBO also liaised with other H2020 projects: CHE, VERIFY, HOLDON and LEMON. SCARBO scientific and technical achievements were disseminated via a project public Website and Twitter channel. The project was also promoted by scientific and industrial partners via conferences, workshops, congresses and technical papers. SCARBO outcomes were published in a White Paper and presented at the third UAB meeting in September 2021.
